package com.hose.utils;

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.Validate;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.annotation.Lazy;
import org.springframework.stereotype.Component;

/**
 *  以静态变量保存SpringApplicationContext, 可在任何代码任何地方任何时候取出ApplicationContext
 */
@Component
@Slf4j
@Lazy(false)
public class SpringContextUtil implements ApplicationContextAware, DisposableBean {

    private static ApplicationContext applicationContext = null;

    /**
     * 取得存储在静态变量中的ApplicationContext.
     */
    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    /**
     * 根据名字从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型.
     */
    public static <T> T getBean(String name) {
        assertContextInjected();
        return (T) applicationContext.getBean(name);
    }

    /**
     * 根据类型从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型.
     */
    public static <T> T getBean(Class<T> requiredType){
        assertContextInjected();
        return applicationContext.getBean(requiredType);
    }

    /**
     * 检查ApplicationContext不为空.
     */
    private static void assertContextInjected() {
        Validate.validState(applicationContext != null,
                "applicaitonContext属性未注入, 请在applicationContext.xml中定义SpringContextHolder.");
    }

    /**
     * 实现ApplicationContextAware接口, 注入Context到静态变量中，容器启动时框架会自动调用这个方法
     */
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        log.info("注入ApplicationContext到SpringContextHolder:{}"+applicationContext);
        if (SpringContextUtil.applicationContext != null) {
            log.warn("SpringContextHolder中的ApplicationContext被覆盖, 原有ApplicationContext为:"
                    + SpringContextUtil.applicationContext);
        }
        SpringContextUtil.applicationContext = applicationContext;
    }

    /**
     * 清除SpringContextHolder中的ApplicationContext为Null.
     */
    public static void clearHolder() {
        log.debug("清除SpringContextHolder中的ApplicationContext:" + applicationContext);
        applicationContext = null;
    }


    /**
     * 实现DisposableBean接口, 在Context关闭时清理静态变量.
     */
    @Override
    public void destroy() throws Exception {
        SpringContextUtil.clearHolder();
    }
}
